Combine 1/3 cup sugar and cornstarch in a medium saucepan over medium-high heat. Stir in milk, chocolate, and 1 tablespoon butter. Cook and stir until thickened and bubbly. Reduce heat; cook and stir about 2 minutes more.

Beat 2 egg yolks in a medium bowl; gradually stir in about 1 cup of the warm chocolate mixture until smooth (this will prevent the eggs from curdling.) Pour this mixture back into the saucepan; bring to a boil. Cook and stir 2 minutes more. Stir in vanilla.

Pour hot chocolate filling into the baked pie shell.

Combine 1 beaten egg, evaporated milk, 1/2 cup sugar, and 1/4 cup butter in another saucepan. Cook and stir over medium heat until mixture is thickened and bubbly. Stir in coconut and pecans.

Spread pecan mixture evenly over chocolate filling. Cool pie on a wire rack; chill pie thoroughly before serving.